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January 12, 2009

Tropical Rainforests Regrowing As People Leave

by Sam Savage

Scientists at a Smithsonian symposium reported Monday that tropical rainforests are making a comeback, but said the young vegetation may not be capable of consuming as much carbon-dioxide or sustaining as much diverse wildlife as the older trees did.

The debate about the world's tropical rainforests has gone on for years, and is the central theme of this week's symposium at the Smithsonian National Museum of Natural History in Washington.

The talks coincide with efforts by the international community to reach a consensus on how to best combat global warming. Tropical forests, due to their ability to sequester the greenhouse gas carbon dioxide (CO2), are seen as a critical component of the solution.

Greg Asner of the Washington-based Carnegie Institution, a symposium presenter, said that roughly 135,000 square miles, or 1.7 percent, of the original forested areas that were taken down are growing back.

This re-growth had occurred rapidly, he said, with the shady forest canopy closing in after only 15 years as the trees become denser and taller. The forest is now able to provide habitat for creatures adapted to such an environment, such as birds with enormous eyes that are able to see in the dark, leafy forests.

However, research by Joseph Wright of the Smithsonian Tropical Research Institute in Panama and Helene Muller-Landau of the University of Minnesota has complicated the issue of whether the rainforests will indeed survive. The pair reported that the future of tropical forests might be more promising than some experts believe, primarily because people who once lived in or near these forests are leaving, allowing vegetation to re-grow.

Wright and Muller-Landau used population projections from the United Nations, and predicted in 2006 that "large areas of tropical forest cover will remain in 2030 and beyond, and thus that habitat loss will threaten extinction for a smaller proportion of tropical forest species than previously predicted."

Maintaining a wide variety of tropical rainforest species is critical as a source for potential pharmaceuticals and disease-resistant crops. However, the scientific consensus is that up to half of all species may be lost in coming years.

But these young forests can't support what the older forests did, according to William Laurence of the Smithsonian Tropical Research Center.

From the Amazon to the tropical woodlands of Africa and Southeast Asia, up to 4.6 million square miles of rainforest have been destroyed by people. This is roughly half of the original tropical forests in the entire world. These forests are now disappearing at the rate of 32 million acres a year, the equivalent of 50 football fields a minute, Laurence told Reuters during an interview before the conference.

"There's just no way that secondary forests are going to capture a lot of the biodiversity and critical ecosystem," he said.

"They're also much more vulnerable to fire."

Laurence believes that people once cleared rainforests for small-scale farming, but this has since being replaced by more destructive large-scale industrial agriculture, mining and logging.